Low temperature synthesis of plasmonic molybdenum nitride nanosheets for surface enhanced Raman scattering

Abstract

Molybdenum nitride (δ–MoN) is an important functional material due to its impressive catalytic, energy storage, and superconducting properties. However, the synthesis of δ–MoN usually requires extremely harsh conditions; thus, the insight into δ−MoN is far behind that of oxides and sulfides of molybdenum. Herein, we report that ultrathin δ−MoN nanosheets are prepared at 270 °C and 12 atm. WN, VN, and TiN nanosheets are also synthesized by this method. The δ−MoN nanosheets show strong surface plasmon resonance, high conductivity, excellent thermal and chemical stability as well as a high photothermal conversion efficiency of 61.1%. As a promising surface enhanced Raman scattering substrate, the δ−MoN nanosheets exhibit a 8.16 × 10 6 enhanced factor and a 10 −10 level detection limit for polychlorophenol.

Smart design of high‐performance surface‐enhanced Raman scattering substrates

“…Xi et al proposed the flexible film formed by the 2D δ ‐MoN nanosheets with an ultrahigh EFs of 8.16 × 10 6 for R6G due to strong LSPR effect (Figure 11D). 110 The free electron density distribution obtained from the calculation of electron localization functions indicates that the electron gas density is high, and a large number of Mo–Mo metallic bonds are formed, which supports the LSPR process of δ ‐MoN nanosheets (Figure 11E). Besides, the large specific surface area and hot spots generated from the gaps and pores among the nanosheets all contribute to the high SERS performance of δ ‐MoN.…”

“…(F) Raman spectra of 2,5‐dichlorophenol absorbed on the flexible δ ‐MoN nanosheet substrate. Reproduced with permission: Copyright 2020, Springer Nature 110 . SERS, surface‐enhanced Raman scattering…”

Defect engineering in semiconductor-based SERS

“…4b). Similar to MoO2, metallic Mo2N and MoN nanostructures have also reported plasmonic activity [76][77][78] . In addition to molybdenum oxides and nitrides, Ti3O5, TiN and VO2 with high EM activity have also been reported [79][80][81] .…”

3D hierarchically porous magnetic molybdenum trioxide@gold nanospheres as a nanogap-enhanced Raman scattering biosensor for SARS-CoV-2

“…Because of the fundamentality of using an appropriate plasmonic/laser resonance excitation to yield optimal signal efficiency, the local EM field strength dynamics were also calculated at 532 and 785 nm, respectively. The rationalized Mie theory 15,59 can be used to compute the spatial distribution of EF at "hotspots" between spherical dimers of the nanostructure using the framework of the |E| 4 approximation 15,17 . The values of |E| 4 and EF of the nanogap "hotspots" existing in the dimer of the nanostructure reach a maximum of ⁓10 5 for an interparticle distance of 2 nm (Figure 6d-e), at 532 nm excitation (direction of polarization, 0°).…”

“…Meanwhile, the state-of-the-art plasmonic Au or Ag NPs face competition from metal oxide semiconductor nanostructures in SERS technology due to their competitive performance and ability to function as both plasmonic and electroactive semiconductor materials [8][9][10] . Therefore, the development of innovative SERS-based biosensors for reliable biological assays using conventional plasmonic metal NPs is slowly eroding due to contentious stability, biocompatibility, and reproducibility [11][12][13][14][15][16] . Besides, their high costs further limit their practical use.…”